Joule-Thomson Coefficients for Two Natural Gases

Abstract

Abstract Joule-Thomson coefficients for two natural gases were determined atpressures up to 600 lb. per sq. in. throughout the temperature interval between70? and 310?F. From these primary data and available information relating tothe isobaric heat capacities of the components at infinite volume, the heatcapacities of these gases were computed throughout the abovementioned range ofpressures and temperatures. The enthalpies of the gases were computed as afunction of state and the results compared with values obtained by severalmethods of prediction currently available. Introduction Experimentally determined Joule-Thomson coefficients for natural gasesafford a satisfactory means of checking the accuracy of prediction of theirthermodynamic properties from the behavior of the components in the pure stateand in binary mixtures. Relatively small samples of these natural gases wereavailable, together with their analyses, and the Joule- Thomson coeffi cients were investigated at temperatures from 70? to 310?F. throughout as largea range of pressures as the quantities of gas on hand permitted. Method and Materials The Joule-Thomson coefficients were determined by measuring the change intemperature resulting from the passage of the gas through a porous thimble witha known pressure difference and under such conditions that the process wassubstantially isenthalpic. The details of the apparatus employed for thispurpose have been described. It is believed that the changes in temperature andpressure were ascertained with an uncertainty of not more than 0.3 per cent.However, as a result of deviations from steady flow, it is probable thatuncertainties as large as 2 per cent may exist in the measured Joule-Thomsoncoefficient. The gases utilized in this work were taken from high-pressure separators andwere dried prior to use by passage over calcium chloride at pressures in excessof 300 lb. per sq. in. The gases were subjected to the conventionalfractionation and Orsat analyses. The results are recorded in Table I. Thecomposition is typical of gases from such sources, with the possible exceptionof the presence of significant quantities of carbon dioxide in each of thesamples. T.P. 1504